The present invention relates to the implantation of one or more prosthetic valve(s) in the pulmonary vein(s) of a subject as a means of decreasing or preventing an increase in pulmonary venous pressure. The present invention accordingly provides novel strategies for the treatment of medical disorders associated with elevated pulmonary venous pressure, including congestive heart failure, as well as for prosthetic pulmonary vein valves and their delivery systems. Expandable as well as fixed-dimension non-expandable pulmonary vein prosthetic valves for implantation by a variety of surgical and percutaneous procedures are also described.
Certain larger veins in the lower extremities of human beings normally have valves that, under conditions of normal function, permit movement of blood largely only toward the heart. In effect, properly functioning venous valves in the lower extremities protect, or partition, the veins of the lower extremities from the relatively high hydrostatic pressure of the column of venous blood between the right atrium and the lower extremities due to the effect of gravity during upright posture. Thus, normally, when upright posture is assumed, venous blood pressure in the foot is generally less than the sum of relatively low pressure in the right atrium and relatively high hydrostatic pressure of the column of venous blood between the right atrium and the foot due to the effect of gravity. When these venous valves in the lower extremities are incompetent, venous blood pressure in the foot becomes predominantly equal to the sum of the relatively low pressure in the right atrium and relatively high hydrostatic pressure of the column of venous blood between the right atrium and the foot, often resulting in pathologic dilatation of the veins in the lower extremities and/or edema.
A prosthetic valve is an endoprosthesis typically formed of biological, synthetic or composite material, the final deployed diameter of which is suitable for implantation in the intended location in the heart or vascular conduits, such as arteries or veins. A prosthetic valve, when implanted and operating as intended, predictably directs the flow of blood through it. For example, a prosthetic aortic valve allows expulsion of blood from the left ventricle into the aorta during systole, and prevents reflux of blood into the left ventricle from the aorta during diastole. When used for replacement or repair of diseased native cardiac or vascular valves, prosthetic valves may relieve inappropriate obstruction to normally directed blood flow by narrowed or stenotic valves, or may restore appropriate hindrance to abnormally directed blood flow caused by leaking or regurgitant valves. Prosthetic valves are usually implanted by means of open surgical procedures, under general anesthesia and often with ventilatory and circulatory support, in which a surgeon exposes a diseased target valve to be replaced, resects and removes it, and implants an appropriate prosthetic valve in its place. Various types and designs of prosthetic valves for diverse clinical applications related to damage to and/or inappropriate function of the native cardiac valves have been described since the original report by Hufnagel et al., 1954, Surgery 35:573. A number of United States Patents have been issued relating to methods for percutaneous delivery of prosthetic valves and associated delivery methods, including, but not limited to, U.S. Pat. No. 5,332,402 by Teitelbaum, U.S. Pat. No. 5,397,351 by Pavenik et al., U.S. Pat. No. 5,607,465 by Camilli, U.S. Pat. No. 5,855,601 by Bessler et al., U.S. Pat. No. 5,163,953 by Vince, and U.S. Pat. No. 5,411,552 by Andersen et al.
In human beings there usually are four pulmonary veins, two left and two right, draining into the left atrium. Pulmonary veins are not known to have directional valves in humans or other mammals. Under normal conditions, the pressure at a site in the pulmonary veins is, with a phase shift dependent on the distance from the left atrium, essentially the same as the pressure in the left atrium. Thus, protection, or partitioning, of the pulmonary veins from the high systolic pressure of the contracting left ventricle is the same as the protection of the left atrium, and is dependent upon proper function of the mitral valve.
The mitral valve may become regurgitant due to damage or malfunction of the valve leaflets, the annulus, the chordae tendinae, or the papillary muscles, or because of dilatation of the left ventricle. When mitral valve function is compromised, partitioning of the left ventricle during systole from the left atrium, and therefore from the pulmonary veins, becomes impaired. As a result, relatively high left ventricular systolic pressure is transmitted, with a phase shift, into the pulmonary veins, often producing marked elevation of the mean pulmonary venous pressure, which can lead to pulmonary edema and congestive heart failure (xe2x80x9cCHFxe2x80x9d).
CHF is a major cause of cardiovascular morbidity and mortality, affecting tens of millions of patients worldwide. Current treatment of chronic CHF often relies on life-long medical therapy. CHF is a complex syndrome of various etiologies associated, in some patients, with abnormally high pulmonary venous pressures at rest and/or in conjunction with physical, emotional or metabolic stress. Whenever possible, CHF largely due to mitral regurgitation is treated with surgical replacement of the mitral valve with a prosthetic valve. In a substantial number of patients, surgical valve replacement is not possible, or is associated with an unacceptably high risk of morbidity and/or mortality.
In certain patients the left ventricle may become non-compliant, or stiff, due to a variety of conditions such as, but not limited to, ischemic heart disease, hypertension, aortic stenosis, diabetes mellitus or aging. In other patients, the mitral valve becomes narrowed or stenotic and fails to open properly during diastole. Transfer of blood into a non-compliant left ventricle or across a stenotic mitral valve during diastole can only be effected when the left atrial, and therefore pulmonary venous, diastolic pressure is markedly elevated. In such patients, signs and symptoms of CHF may develop due to markedly elevated diastolic and mean pressure in the left atrium which is transmitted to the pulmonary veins. To date, CHF due to diastolic left ventricular dysfunction can only be treated with medications, with variable efficacy. Mitral stenosis can be relieved in most patients by surgical or balloon commissurotomy or with mitral valve replacement.
The present invention generally relates to a novel strategy for treatment of disorders associated with elevated pulmonary venous pressure involving implanting, in a subject, one or more endoprosthesis (xe2x80x9cvalvexe2x80x9d), preferably in or at the ostia of a pulmonary vein(s).
It is an object of this invention to provide for methods and devices which lower mean pulmonary venous pressure, and thereby treat conditions such as congestive heart failure (xe2x80x9cCHFxe2x80x9d), by creating an effective unidirectional partitioning between the left atrium and one or more of the four pulmonary veins. The present invention provides for expandable as well as fixed-dimension prosthetic valves for implantation in or at the pulmonary veins of appropriately selected patients with existing, impending or probable CHF.
The prosthetic valves of the invention, in their properly implanted condition, configuration and orientation, are capable of permitting ingress of blood from the pulmonary vein(s) into the left atrium during that portion of the cardiac cycle when the pressure in the pulmonary vein(s) slightly exceeds the pressure in the left atrium, and are capable of preventing egress of blood from the left atrium into the pulmonary vein(s) during that portion of the cardiac cycle when the pressure in the left atrium slightly exceeds the pressure in the pulmonary vein(s).
In further embodiments,the present invention relates to particular species of expandable prosthetic pulmonary valves, to said valves comprised in delivery systems, and to strategies for percutaneous or surgical delivery, placement and implantation of said valves. Specific examples include the diaphragm, trapdoor, stocking and windsock valves illustrated in FIGS. 1-4, respectively.
In preferred embodiments of the invention, pulmonary vein prosthetic valves, when implanted in one or more pulmonary vein(s), are intended to relieve or eliminate CHF due to mitral valve regurgitation and/or left ventricular non-compliance. In patients with CHF with abnormally high mean pulmonary venous pressure due to defective systolic partitioning between the left ventricle and the pulmonary veins largely or partially secondary to mitral regurgitation, who are deemed unsuitable for mitral valve replacement, implantation of prosthetic pulmonary vein valves may be used to lower mean pulmonary venous pressure by restoring effective systolic partitioning between relatively high left ventricular and left atrial systolic pressure, and pulmonary veins. In patients with CHF largely or partially due to left ventricular diastolic dysfunction or mitral stenosis, with abnormally high mean pulmonary venous pressure due to natural lack of diastolic partitioning between the left atrium and pulmonary veins, implantation of the prosthetic pulmonary vein valves may be used to lower mean pulmonary venous pressure by creating effective diastolic partitioning between relatively high left atrial diastolic pressure and the pulmonary vein(s).